There has been considerable interest within the detergent industry for solid laundry and dish washing detergents which are “compact” and therefore, low dosage volumes are in demand for effective laundering and dish washing operations. To facilitate production of these so-called low dosage detergents, following three important conditions have to be fulfilled.                1. Detergent particles containing high concentration of detergent or surfactant active(s);        2. Detergent particles of high bulk density, for example with a density of 600 g/l or higher; and        3. Non-sticky and free-flowing detergent particles.        
Generally, there are three primary types of processes by which solid detergents either granules or powders can be prepared. The first type of process involves spray-drying an aqueous detergent slurry in a spray-drying tower to produce highly porous detergent granules (e.g., tower process for low density detergent compositions). The second type of process involves spray-drying an aqueous detergent slurry in a spray-drying tower as the first step, then, the resultant granules are agglomerated with a binder such as a nonionic or anionic surfactant, finally, various detergent components are dry mixed to, produce detergent granules (e.g., tower process plus non-tower [agglomeration] process for high density detergent compositions). In the third type of process, the various detergent components are dry mixed after which they are agglomerated with a binder such as a nonionic or anionic surfactant, to produce high density detergent compositions (e.g., non-tower [agglomeration] process for high density detergent compositions).
Due to excellent detergent properties and high biodegradability, alkyl ether sulfates are the preferred and most widely used surfactant actives in compact laundry detergent compositions. Alkyl ether sulfates are known to be used in detergent compositions in aqueous solution or paste form. However as it is necessary to control the ratio of liquids to solids in order to form detergent granules, the maximum level of surfactant active material which may be incorporated in this manner is limited. Also, alkyl ether sulfates are highly heat sensitive and therefore cannot be processed at elevated temperatures because of a tendency to decompose significantly at temperatures higher than 80° C. Therefore, they are not generally incorporated into spray-dried laundry powders via the slurry.
It is therefore desirable to incorporate these alkyl ether sulfates as a separate solid component to manufacture the compact laundry detergent compositions. Agglomeration is one such method wherein surfactant active material is dry mixed with other detergent components to prepare the solid detergent compositions. However, it has been still not possible to produce solid detergent compositions comprising high concentration of surfactant actives such as alkyl ether sulfates.
High levels of surfactant actives are required in laundry detergent compositions, particularly in compositions intended for washing by hand, to give effective soil removal. However, it has been found that problems of poor powder properties can be encountered in high-active compositions, for example, powder stickiness leading to agglomeration and poor flow. Hence, many prior arts mention about producing low active of less than 40% of surfactant active ingredients.
U.S. Pat. No. 6,221,831 (Unilever) describes use of low amount of about 7% maximum of detergency builders such as zeolites and the active anionic surfactant claimed is at least 27%.
Indian patent application no. 2623/MUM/2009 (Hindustan Unilever Ltd.) describes a free-flowing detergent granules comprising 10-30% of anionic surfactants.
U.S. Pat. No. 5,916,868 (Church & Dwight Co.) relates to a process for the production of a free-flowing high bulk density granular laundry detergent product comprising up to 40% of surfactant.
EP 105 160A (Akzo) discloses silicas loaded with aqueous surfactant solutions, preferably primary alcohol sulfate, alkyl ether sulfate or nonionic surfactant, for use in toothpastes; the highest surfactant loading disclosed in a free-flowing granule is 20 wt %, higher loadings being detrimental to flow.
Another requirement for preparing compact detergent is to have high bulk density.
There are prior arts which teach the preparation of both high bulk density and low bulk density detergents. IN 214078 (P&G) describes the process of producing a low density detergent composition which is having a density of less than 600 g/l.
Detergent compositions having a high bulk density are typically prepared by a process involving mixing or granulation of components of the composition and/or a base powder obtained for example from a spray-drying process and provide significant consumer benefits as compared to compositions of lower bulk density.
It is also known to incorporate anionic surfactant e.g. fatty alkyl ether sulfates in detergent compositions by means of a solid adjunct, that is, a particle comprising the surfactant and other components of the composition e.g. sodium carbonate and a builder. Hitherto, the level of anionic surfactant present in such adjuncts has been limited due to the need to provide good flow properties and to reduce the tendency to agglomerate.
There have been many attempts on achieving solid particles having high loading of alkyl ether sulfates and that too maintaining the free-flowing nature of the particles.
EP 430 603A (Unilever) discloses detergent granules containing at least 30 wt % anionic surfactant and a highly oil-absorbent filler, for example, a silica, in intimate contact with the anionic surfactant.
EP 651 050A (Procter & Gamble) discloses detergent agglomerates comprising a solid, preferably water-soluble, a salt (for example, sodium silicate, carbonate or sulfate), and a fluid binder comprising an anionic surfactant (preferably alkyl ether sulfate) and sodium silicate.
U.S. Pat. No. 6,369,020 (Unilever) teaches to prepare free-flowing granular detergent component comprising at least 30%, preferably 30-75% of alkyl ether sulfates.
WO 97 10321A (Procter & Gamble) discloses structured surfactant compositions comprising 35-60 wt % surfactant, preferably alkyl ether sulfate, 1-20 wt % hydrophilic finely-divided silica and 15-25 wt % moisture; these compositions are in the form of a “hardened continuous paste”.
Thus, although there have been many attempts to prepare solid, high active alkyl ether sulfate compositions but still there is a need to have even more high active i.e. at least 50% active content, preferably more than 60% and more preferably more than 70% and even more preferably more than 75% which was not possible in the prior art processes/compositions. Also, all the prior arts teach about heating alkyl ether sulfates at temperature lower than 80° C. to avoid its decomposition.
In accordance with the above, the inventors of the present invention have surprisingly found a unique process to produce free-flowing, solid, highly concentrated alkyl ether sulfates by processing it at temperature of above 80° C. through unique combination of zeolites, carbonates, structurant and coating material. These solid, high active alkyl ether sulfates then can be used in combination with other detergent adjuvants to prepare the final detergent formulations or can be directly used as final detergent formulations.